Touch sensor

ABSTRACT

A touch sensor using a Hall IC is provided. To this end, in a cantilever mechanism  15  of a parallel link by two plate springs  16,  a coupling member  18  on the fixed side is fixed to a supporting block  24  which penetrates through the center of a plate spring  16  on a lower side and uprightly provided on a pedestal  22.  A movable portion  28  on the free end side is a lightweight coupling member  19  provided by bend-processing an aluminum thin plate, to which a rare-earth magnet  25  is adhered. An elastic part  20   a  of a Hall IC supporting member  20  is fixed to the coupling member  18  on the fixed side, and a rigid part  20   b  with a rib  17   a  is supported by an adjusting rod  36  to fine-adjust relative position of a Hall IC  26  provided on the free end with respect to the magnet  25.  Elastic wire materials  38   s  are fixed to the Hall IC supporting members  20   s  which hold at a free end  38   b  the self-weight of the movable portion  28,  and abutted with a lower surface  40   a  of a bush on the inner surface of a housing  12,  so that the movable portion  28  is stabilized in its position. A light load of 0.6 gf or less activates an anvil  34,  and the Hall IC  26  detects a minute displacement of 0.1 mm or less of the magnet  25,  in order to light up a signal light  14.

FIELD OF THE INVENTION

The present invention relates to a touch sensor aiming to correct anerror of process dimension due to abrasion of an edge tool by setting areference position for checking the machining position while the cuttingedge of the edge tool such as a bite and drill in an automatedcomputer-controlled machine tool such as a machining center and a jigdrilling machine advances. More specifically, the invention relates to aconstruction of a mechanism that enables it to detect a minutedisplacement (in microns or sub-microns) with a minute measuringpressure.

BACKGROUND ART

In recent years, IC integration level has increased dramatically. Thisrequires further minute precision hole processing, for example,accurately depth-processing 2-4 layers out of 5-6 layers of printedboards in the order of micro-meter, using a drill made of an ultra-hardmaterial such as diamond having a diameter in the order of 0.1 mm orless. The revolution speed of the drill reaches hundreds of thousandsper minute, causing abrasion to occur at the cutting edge. Therefore,the edge position must be checked regularly, e.g. every one hundredtimes of hole processing, in order to keep the relative position betweenthe working table and the cutting edge constant.

A touch sensor is used as a checking apparatus for keeping the cuttingedge stable with respect to a reference position provided as apredetermined height from the surface of the working table of theaforementioned machine tool. It is provided with a mechanical means forswitching an electric contact from ON state to OFF state by a snapaction of, e.g. toggle mechanism, when a free end of a lever-typeactuator rotatably supported by a hinge is pressed against an edge tool,and its movement is transferred to a sliding pin. Alternatively, it maybe provided with an optical means wherein the reference position of theedge is detected with a signal output at which the edge directly blocksthe light beam, to correct the fluctuation due to the abrasion at theedge.

However, a contact load for activating a touch sensor having amechanical means requires e.g. 100 to 300 gf as an energizing force inorder to counteract resistance by anti-action accompanied with a snapaction of a contact by moving the actuator lever. Accordingly, withoutsuch a contact pressure, a setting of a reference position with accuracyand stable reproducibility is not obtained. On one band, processing adiameter of 0.1 mm or less in the order of 0.01 mm using a diamond drillrequires a touch sensor with a very light contact pressure, becauseactivating a touch sensor with a contact load as described above maycause the drill itself to bend at a buckle, resulting in unstableposition setting of the drill tip, thereby damaging reproducibility.

On the other hand, detecting directly the tip of a cutting tool by anoptical method involves no contact and does not require a settingpressure. But it has a disadvantage that it is difficult to respond tovariations in the cutting edge form, because the method has so manyadjusting parts for making adjustments, which depend on thecharacteristics of the electronic circuit, such as adjustments ofreproducibility, neutral zone, light amount, and temperature change, sothat it is inconvenient for handling and vulnerable to dust.

Therefore, an object of the invention is to provide a touch sensorhaving a contact load of 0.5 gf or less as an operation force,reproducing sensitivity or precision in the range of ±0.5 μm, freedom ofattaching to and detaching from the working table of the automatedmachine tool, and furthermore ease of handling the reference positionsetting.

DISCLOSURE OF INVENTION

To achieve the object mentioned above, a touch sensor according to theinvention is characterized by comprising,

-   -   a first coupling member 18 constructed in a united manner with a        pedestal 22,    -   plate springs 16 arranged to be parallel to each other, one end        sides of the plate springs being fixed to both ends of the first        coupling member 18 respectively,    -   a second coupling member 19 to couple other ends of the plate        springs 16 s to each other,    -   a magnet installed in a manner that the side of each plate        spring corresponds to the side of either magnetic pole,    -   a pipe mounted to each plate springs 16 in parallel to the        direction of the magnetic poles of the magnet 25, and    -   a detecting means located near the magnetic pole boundary line        of the magnet 25 and detects a displacement of the magnet 25        caused by an external force applied to the pipe 30,    -   wherein the each plate 16 has a rigid part with rigidity on the        base end side, and an elastic part with elasticity on the both        end sides.

Furthermore, the touch sensor comprises elastic bodies 38 s to cancelthe effect of gravity on the second coupling member 19.

The touch sensor comprises,

-   -   a supporting member 20 having one end side fixed to the first        coupling member 18 and other end side provided with the        detecting means 26 or the magnet 25, the supporting member 20        being inclined from the one end side to the other end side, and    -   an adjusting member 36 for adjusting the distance between the        supporting member 20 and the pedestal 22,    -   wherein the magnet 25 or the detecting means 26 is mounted to        the second coupling member 19.

Moreover, holes are provided to portions 16 and 19 where displacement iscaused by an external force applied to the pipe.

One end of the pipe 30 is provided with a rigid anvil 34 to receive anexternal force.

The touch sensor comprises a notifying member for notifying whether ornot a signal is output from the detecting means 26.

Pedestals 22 are provided to at least two parts on a bottom surface ofthe pedestal 22.

The pipe is provided with a regulating member 35 for regulating adisplacement of pipe body 30.

Alternatively, the pipe 30 is provided so that its other end regulates adisplacement of the pipe body 30.

That is, the touch sensor according to the invention uses a Hall IC todetect a minute displace of 0.1 mm or less of the small-size magnetwhich is displaced integrally with the parallel displacement of theanvil caused by a light load of 0.5 gf or less, so as to provide anopen/close control of an electric circuit. The parallel displacement isbasically provided by a parallel-link cantilever mechanism consisting ofa dual structure by plate springs having the same shape, wherein,

-   -   any of the plate spring is an empty frame having a rectangular        shaped plan skeleton,    -   polyimide thin plates forms a shape provided by elastic arms of        a same length extended in a parallel manner in an elongated        direction from each of the four corners of the skeleton, and    -   an aluminum alloy thin plate with the same shape as the skeleton        and a rib provided to protrude along the inner circumferential        edge defining a rectangular space of the empty frame, is adhered        to the skeleton so as to render the skeleton part a rigid body.

The coupling member for the plate springs on the fixed end side in thecantilever mechanism is fastened on the supporting block provideduprightly at the central part of the pedestal through the empty portionof the plate spring. The coupling member for the plate springs at thefree end in the cantilever mechanism is formed in a U-shape bybend-processing an aluminum alloy thin plate, and its weight isdecreased by boring holes. A tube material of a small diameterperpendicular to the plate springs penetrates the upper and lowersurfaces of the U-shape and joins as a pipe with the surfaces. Thesmall-size magnet is fastened to a predetermined position near thecenter of the coupling member at the free end, while opposed to thesmall-size magnet, a Hall IC is positioned to the free end of thesupporting member provided and fixed to the coupling member on the fixedend side and extended.

In addition, an adjusting rod provided to the supporting block inhibitsthe supporting member from making an elastic deformation inclined fromthe fixing position to the pedestal, enabling to forcibly displace theHall IC to a position where it is opposed to the small-size magnet, andenabling a fine-adjustment in the direction of the rod axis by means ofthe screw action of the adjusting rod. A signal light is provided andfixed to the supporting member.

There is provided with a molded housing totally surrounding thecantilever mechanism to form on the top surface of the pedestal aperipheral wall of a hermetical fitting stage for an inner surface ofthe bottom aperture of the molded housing. The molded housing isprovided on the top surface with an aperture of a large diameter throughwhich the pipe is inserted and a window having a transparent cover torender the signal light visible, and on the side surface with an openingthrough which an electric wire material is pulled out. At the formingsurface for the large diameter aperture, a flanged boss facing thelock-washer is provided and fixed on the outside, and on the inside abush to abut with and position the free end of the parallel link.

Furthermore, the anvil and the lock-washer are fastened to a tubematerial of a large diameter fitting the outer diameter of the tubematerial of a small diameter as the pipe, whereby the anvil is freelydetachable from the pipe while the lock-washer regulates downwarddisplacement of the pipe. As a positioning member for causing the freeend of the parallel plate spring to abut with the bush, an elastic bodyis provided in a tensioned manner between the fixed and free ends of theparallel link in order to yield a force in the direction to cancel theeffect of gravity acting on the construction at the free end, and thusrestrain an inertia movement. The pedestal is provided with an extendedpart overhanging from the wall around the fitting stage to the exteriorof the housing, and pedestals are drilled at at least two appropriatepositions on the bottom surface.

According to the touch sensor of the invention, in order to set areference height of the cutting edge from the working table surface, theanvil contacting with the cutting edge is subject to a parallel movementby means of the parallel link mechanism of the cantilever beams of theparallel plate springs made of polyimide thin plates. Furthermore, themovable portion of the parallel plate springs is made of aluminum alloythin plates and a tube material with a small diameter, so that itsweight is decreased. Thus, it is made possible to set the referenceheight using a contact load substantially of 0.3 gf or less, so thatload is hardly applied to the edge tool.

With the Hall IC detecting the movement of the magnet caused by theparallel movement of the anvil, it is enabled to detect a displacementat a reproduction precision of ±0.5 μm or less to renew the defaultposition setting the cutting edge. Further, the parallel plate springhas an empty skeleton through which space the supporting block at thefixed end of the cantilever beam is penetrated and constructed, and thusallowing a compact package of the total touch sensor. The movableportion of the parallel plate spring has its self-weight supported by acantilever elastic wire material and abuts with the bush fixed insidethe housing, which allows a compact construction as well as the movableportion of the parallel plate spring to be held stably.

Furthermore, since the elastically displaced position of the Hall ICsupporting member is normally held by the adjusting rod, it is madepossible to fine-adjust the relative position between the Hall IC andthe magnet to a position indicating the optimal sensitivity, controllingthe screw part of the adjusting rod renders. The anvil is freelydetachable from the pipe, so that it can be easily replaced whenabrasion or deformation occurs. Such a touch sensor can always beinstalled to a predetermined position on the working table by means ofthe knock hole drilled on the pedestal, it is made possible for anappropriate clamp to be engaged with and easily bolted to the extendedpart over-hanged to the exterior of the housing.

Further, it is possible to prevent the parallel plate springs fromdeforming excessively to a level exceeding an elastic limit, because thelock-washer fixed untidily to the anvil abuts with the flanged bossfixed to the top surface of the housing so as to limit the anvilmovement, and the signal light enables the operation of the Hall ICvisible. Moreover, no degradation due to abrasion will occur, becausethe magnet of the movable portion and the Hall IC of the detecting partare not in contact to each other, and since joints of the parallel linkare the plate springs, there is no friction, i.e. no deterioration dueto friction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a touch sensor according to theinvention. Figs. (a) and (b) respectively shows a side view and a crosssection taken along line B-B of Fig (a).

FIG. 2 is an illustration of a plate spring to construct a parallel linkin the touch sensor according to the invention, (a) a plan view, (b) across section taken along line B-B of (a), and (c) an expanded view ofthe part of (b) circulated with a sign c attached to it.

FIG. 3 is a bottom view taken along line III-III of FIG. 1(a).

FIG. 4 is a perspective view of FIG. 1, parts thereof beingdisassembled.

FIG. 5 is an operational illustration of a touch sensor in accordancewith the invention, a housing and a signal light being removed.

FIG. 6 is a descriptive view of a cantilever mechanism by two parallelplate springs in a touch sensor according to the invention, (a) being apartial view of an embodiment and (b) a schematic view.

FIG. 7 is a side view of an expanded illustration of the relationshipbetween a Hall IC and a magnet in a touch sensor according to theinvention.

In those Figures, plate thicknesses are always exaggerated.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of a touch sensor according to the invention willbe now described in detail hereinafter based on the drawings. FIG. 1shows an embodiment of a touch sensor 10 according to the invention, (a)a side cross-sectional view and (b) a cross-sectional view along lineB-B of (a). FIG. 2 is a plan view to illustrate one of two parallelplate springs 16 of the same shape which are constructedmirror-symmetrically opposed to each other having a same geometry, (b) across-sectional view along line B-B of (a), and (c) an expanded view ofthe part of (b) circulated with a sigh c. FIG. 3 is a bottom view alongline III-III of FIG. 1(a). FIG. 4 is a perspective view of FIG. 1, partsthereof being disassembled. FIG. 5 is an operational illustration of thetouch sensor 10 of FIG. 1, a housing 12 and a signal light 14 beingremoved. Note that plate thicknesses are all exaggeratedly illustratedin the drawings.

In FIG. 1, a cantilever mechanism 15 which is a major member of thetouch sensor 10 is a type of parallel link mechanism (see FIG. 6(b))constructed by the two plate springs 16 having the same shape. As shownin a plan view in FIG. 2(a), a plate spring 16 is a formation ofpolyimide thin plate member (having a thickness of about 75 μm) shapedby a rectangular empty frame 16 a, from four corners of which, elasticarms 16 bs, elastic parts, are respectively extended in parallel in alongitudinal direction. Further, an aluminum alloy thin plate 17, arigid part, is matched and adhered to each plate spring skeleton 16 a(see FIG. 2(b) and (c)), the plate 17 being molded into an empty framehaving the same plan shape as the skeleton 16 a, and provided with a rib17 a cut and raised by burring along an inner circumferential edge so asto protrude from it. This turns the skeleton 16 a of each plate spring16 into a rigid structure, with only the part of each elastic arm 16 bfunctioning as a movable portion. The thus constructed two plate springs16, 16 having the same shape are spaced in parallel at an appropriatedistance in upward, downward, and lateral directions, and opposedmirror-symmetrically to each other. The ends of the both springs arerespectively combined by coupling members 18, 19 which are rigid bodiesperpendicular to each plate spring 16.

In the cantilever mechanism 15 indicated in FIG. 6(a), the upward anddownward displacements at free ends of the parallel plate springs 16, 16are provided by curvature of four elastic arms 16 b extended form theskeleton 16 a. That is, the parallel link mechanism by four rigid barbodies a, b, c, d shown in the schematic view of FIG. 6(b) is equivalentto one of FIG. 6(a), and a joint k in FIG. 6 corresponds to the elasticarm 16 b circled by a two-dot chain line in FIG. 6(a). In the parallellink construction in FIG. 6(b), the upward and downward movement at afree end c causes rotational friction to occur between a shaft and abearing that construct the joint k, while at the elastic arm 16 b anelastic deformation absorbs the upward and downward movement and thus nofriction occurs. Accordingly, neither load fluctuation due to friction,nor friction lose and abrasion will occur.

The coupling member 18 on the fixed end side of the parallel platespring 16 in the cantilever mechanism 15 is advantageously a moldedblock of a ferrous material, considering expansion coefficient of themember having to be approximated to one of the processing machine towhich the member is to be equipped for use. However, sleight of thecoupling member 18 may be decreased using an aluminum alloy or asynthetic resin depending on purpose of use. The coupling member 18 onthe fixed end side has two columns 18 d, 18 d extending from the bothsides of a central pedestal 18 a. Each of the columns has mountingsurfaces on a top surface 18 b and a lower surface 18 c onto which theend of the elastic arm 16 b of the parallel plate spring 16 isscrew-combined and fixed. The two columns 18 d, 18 d are formed so thatthe extended portions above a seat surface 18 e of the central pedestal18 a are sufficiently long. The seat surface 18 e is provided as amounting seat for a Hall IC supporting member 20 described hereinafter(see FIG. 1(b)).

A ferrous molded supporting block 24 is screw-combined from the lowersurface and fixed to a mounting seat 22 a provided to the top surface ofthe ferrous molded pedestal 22 to protrude from it, which is formed forthe same reason as above (see FIGS. 1 and 3). As to the supporting block24, as illustrated in FIG. 5, an upright portion 24 a on the mountingseat 22 a penetrates the rectangular empty space formed in the platespring 16 positioned at the lower side, so that a transverse beam 24 bextends in parallel with the mounting seat 22 a through the middleposition spaced apart from the both upper and lower parallel platesprings 16, 16. The transverse beam 24 b intrudes into a penetrationhole 18 f provided by drilling the middle pedestal 18 a of the couplingmember 18 on the fired end side, so that the upper and lower surfaces 18b, 18 c of the column 18 d to be the fixing surfaces for the parallelplate springs 16 s are provided and fixed to the mounting seat 22 a inparallel. Under this condition, the free end of the cantilever mechanism15 is elastically deformed to a position where the elasticity of theelastic arms 16 b of the two upper and lower parallel plate springs 16come to balance with the action of gravity m to be supported (see FIG.6(a)).

As shown in the perspective view of FIG. 4, the coupling member 19 onthe free end sides of the parallel plate springs 16 in the cantilevermechanism 15 is provided by outwardly bend-processing upper and lowerparts of a lightweight aluminum alloy thin plate, and conjugating theparts to the free ends of the elastic arms 16 b of each parallel platespring 16. That is, forming U-shaped structure in section comprising twoparallel upper and lower surfaces 19 a, 19 b provides the couplingmember 19 on the free end sides with rigidity. Moreover, in order todecrease the weight, suitably shaped holes 19 c, 19 d are provided on avertical surface 19 e by drilling. On the vertical surface 19 e, apocket 19 f is cut out to match the circumference of a small-sizerare-earth magnet molded in a cube form 25 with its top surface side isprovided as the South pole, the magnet 25 is adhered to a seat surface19 g provided by bending the lower hem at right angle to be cut andraised, and a surface 25 a comprising South and North poles on the upperand lower sides respectively is opposed to a detecting surface 26 a ofthe Hall IC 26 provided and fixed to the free end of the Hall ICsupporting member 20 installed inside of the pocket 19 f.

In the perspective view of FIG. 4, positioning is performed withpedestals 16 cs provided by drilling the free ends of the elastic arms16 bs on the free end sides of the parallel plate springs 16 s, andpedestals 19 hs provided by drilling each of both ends of the topsurface 19 a and the lower surface 19 b of the coupling member 19 at thefree end side. The top surface 19 a and the lower surface 19 b of thecoupling member 19 on the free end side are thereby adhered to the freeends of the elastic arms 16 bs on the upper and lower free end sides.Thus, the free ends of the two upper and lower parallel plate springs 16are coupled to the coupling member 19, so that a movable portion 28 ofthe cantilever mechanism 15 is formed.

A pipe 30 is adhered to the movable portion 28, the pipe 30 penetratingthrough the central part of the top surface 19 a and the lower surface19 b of the coupling member 19 at the free end side, and beingperpendicular to the mounting seat 22 a of the molded pedestal 22. Tolightweight the movable portion 28, the pipe 30 is preferably a thinstainless tube, and the coupling member 19 is lightweighted by providingholes inside. The upper end of the pipe 30 is long enough to protrudefrom the housing 12 described hereinafter, and relates to the setting ofa reference height H from the working table surface F.

On the top surface of the pipe 30, an anvil 34 formed of pure aluminumon which surface highly rigid material such as sapphire, ruby anddiamond is provided, is attachably/detachably provided to provide a flatcontact surface 32 directly contacting with the cutting edge (not shown)of a measuring object and determining the reference height. That is, theanvil 34 is constructed such that it is adhered to a thin stainless tuberib 34 a of a large diameter slidably fitting the outer diameter of thethin stainless tube forming the pipe 30, together with a lock-washer 35functioning as a stopper. The lower end of the pipe 30 may be providesas a stopper to set a distance from the top surface of the moldedpedestal 22 to limit the lower movement range of the movable portion 28.

As shown in FIG. 5, the Hall IC supporting member 20 comprises anelastic part 20 a whose end part is fixed to the seat surface 18 e ofthe pedestal 18 a at the center of the coupling member on the fixed endside, a rigid part 20 b forming a structure by bending downwardly theboth lines along the longitudinal direction, and an adhering seat 20 cof the a Hall IC26 formed by bending downwardly the free end. Theelastic part 20 a is fixed to the seat surface 18 e of the centralpedestal 18 a, with the rigid part 20 b forcibly deformed and inclineddownwardly by a snail angle (e.g. 40 degrees) as shown by the two-dotchain line in the drawing.

The slightly inclined rigid part 20 b of the Hall IC supporting member20 is supported at an upper end 36 a of an adjusting rod 36 screwed toan appropriate position on the top surface of the supporting blockupright portion 24 a, and raised to an nearly horizontal position inorder to move the Hall IC detecting surface 26 a to an area that reactsto the flux of the magnet 25. The axially-directed upward and downwardmovement due to the screwing action of the adjusting rod 36 allows afine adjustment of the optimal activating position of the Hall IC26. Byfixing the supporting block 24 to the pedestal 22 after the positionadjustment of the Hall IC 26 is completed, the pedestal 22 conceals ahead part 36 b to control the axially-directed movement of the adjustingrod 36. This makes it impossible for the rod to be controlledexternally, so that once the optimal position of the Hall IC26 isadjusted, it can not be intentionally modified. Additionally, as shownin FIGS. 1 and 4, the signal light 14 of a light emitting diode isprovided and fixed to the Hall IC supporting member 20 so that it ispossible to visualize an activating signal by lighting the signal light14 which is emitted when the Hall IC 26 reacts to a magnetic potentialof a preset threshold value.

Furthermore, as distinctly illustrated in FIGS. 4 and 5, two elasticwire materials 38 s (stainless spring wire materials with a diameter of0.1 mm, the natural shape thereof being illustrated with a two-dot chainline) to compensate the amount of downward natural displacement due tothe weight m (arrow) of the movable portion 28 including the couplingmember 19 the parallel plate spring 16, the magnet 25, the pipe 30, theanvil 34, and the lock-washer 35 in the cantilever mechanism 15, areprovided and fixed to the Hall IC supporting member 20 by an end 38 a inorder to warp an free end 38 b. The wire materials are inserted throughtwo transparent holes 19 i, 19 i provided on the coupling member 19corresponding to the extension lines of the elastic wire materials 38right below the top surface 19 a of the coupling member 19, so that anupward energizing force t (arrow) may be supplied. The imparting force tis much greater than weight m, and the top surface 19 a of the couplingmember 19 is lightly pressed against a lower surface 40 a of a bush 40provided and fixed to the inner surface of the housing 12. This rendersit possible to hold the parallel plate springs 16 almost horizontallyand stably, as well as stably set the position of the magnet 25 in thedirection of the height.

Based on FIG. 1 again, the molded housing 12 totally surrounding thecantilever mechanism 15 will be described. Formed on a top surface 12 aof the molded housing 12 are a window with a transparent cover 41through which the signal light 14 is visible, and a large diameteraperture 42 through which the pipe 30 is position-adjustably inserted. Aflanged boss 43 opposed to the lock-washer 35 mounted to the anvil 34 isadhered to the exterior of the large diameter aperture 42 to limit therange of downward movement of the anvil 34 by the lock-washer 35 and theboss 43 a abutted to each other. To the inside of the large diameteraperture 42, the bush 40 is provided and fixed to loosely fit the pipe30 to regulate the upper limit of the movement of the movable portion 28or the magnet 25, so that the reference position of the anvil 34 is set.

An electric wire pullout opening 45 with a rubber cap 44 is provided ona sidewall 12 b of the molded housing 12 facing the coupling member 18on the fixed end side of the cantilever mechanism 15. Moreover, asidewall circumference surface 12 c of the side wall surrounding themolded housing 12 matches the same surface as the outer circumferentialedge of the molded pedestal 22. Inside the outer circumferential edge 22b of the molded pedestal 22, a fitting stage peripheral wall 22 c isformed to which a fitting inner surface 12 d formed at the bottomaperture of the molded housing 12 is tightly fitted.

As shown in FIG. 3, on a lower surface 22 d of the molded pedestal 22, adrilled hole for accommodating the head of a bolt 24 c for bolting themolded supporting block 24 and a knock hole 22 e for positioning areprovided. Further, on a part of the outer circumferential edge 22 b ofthe pedestal 22, an extended portion 22 f is formed overhangingoutwardly from the fitting stage peripheral wall 22 c to the sidewallcircumference surface 12 c of the sidewall of the molded housing, andengaged with a clamp 46 as illustrated in FIGS. 1(b) and 4. A bolt 47 isinserted through a bolt hole 46 a provided on the top surface, andscrewed to a screw hole 48 carved on the working table surface F, sothat the touch sensor 10 is fixed to the working table surface F.

Now, the touch sensor 10 according to the invention will be describedwith respect to its operation. Instead of a block gage for setting thereference height of the cutting edge of the drill, the touch sensor 10is installed at an appropriate position on the working table F of amachine tool such as a computer-controlled machining center or jigdrilling machine. To this end, a knock pin 49 is implanted and the screwhole 48 is carved at the installing position on the working table F sothat the sensor can be installed at the same position all the time.

The knock hole 22 e for positioning provided on the lower surface 22 dof the molded pedestal 22 of the touch sensor 10 is engaged with theknock pin 49 implanted on the working table F. As shown in FIGS. 1 and4, the clamp 46 is engaged with the extended part 22 f of the moldedpedestal 22 overhanging outwardly from the sidewall circumferencesurface 12 c of the molded housing 12, and then the bolt 47 is insertedthrough the bolt hole 46 a provided on the top surface of the clamp, tobe screwed to the screw hole 48 on the working table F. By tighteningthe bolt 47, the working table F is pressed against the extended part 22f of the pedestal 22 by means of the clamp 46, so that the touch sensor10 is fixed at the defined position.

The reference height H from the working table F to the top surface ofthe anvil 34 is automatically set. For example, in a precision holeprocessing, a drill (not shown) is moved from a processing position to aposition right above the central axis of the anvil 34 of the touchsensor 10. When the drill is descended gradually, the tip of the drillcome into contact with a contacting surface (reference surface) 32 ofthe anvil 34, so that the pipe 30 is downwardly pressed and moved. Theweight of the movable portion 28 of the cantilever mechanism 15 isalmost in balance with the integrated energizing force of the parallelplate springs 16 and the compensating elastic wire materials 38,allowing the load with which the cutting edge of the drill downwardlydisplaces the movable portion 28 via the anvil 34 to be provided as 0.5gf or less. This dispels the concern that the drill may bebuckling-deformed.

As illustrated expandedly in FIG. 7, the surface 25 a of the magnet 25provided and fixed to the coupling member 19 on the free end sideconstructing the movable portion 28, the surface 25 a comprising theSouth and North poles on the upper and lower sides respectively, isopposed to the Hall IC detecting surface 26 a at an adjacent positionwithin the area of the magnetic field M of the magnet 25. The magneticpotential of the magnetic field formed by the magnet 25 is zero on aplane V_(o) which crosses perpendicularly the axis of the magnet 25 atan equal distance from the both magnetic poles S, N. The magnetic powergradually strengthens toward the both poles. In the vicinity of theplane V_(o), the effect of the magnetic force due to a fluctuation ofdistance between the SN surface 25 a of the magnet and the Hall ICdetecting surface 26 a can be ignored, because the magnetic potentialsurface is distributed almost in parallel. Therefore, if the gap betweenthe SN surface of the magnet 25 a and the Hall IC detecting surface 26 ais small enough, accurate fine adjustment is not required.

For this purpose, the threshold value of the Hall IC26 to respond to themagnetic force is set to, for example, 20 gauss (S20 G) on the S-poleside, so that a Hall IC 26 transfers a closing signal to the connectedelectric circuit (not shown) at the moment the magnetic potentialsurface −V₂₀ such as of 20 gauss of the magnet 25 which descendstogether with the coupling member 19 united with the pipe 30 passesthrough, for example, a point P on the detecting surface 26 a. Receivingthis signal, the computer of the machine tool renews the initial settingof the reference position. On the other hand, receiving this signal, thesignal light 14 of the emitting diode also lights up and blinks tonotify that the cutting edge has reached the reference position. By thisoperation, it is rendered possible to monitor and correct the abrasionof the cutting edge all the time, an d to restrain the reproductionprecision to ±0.5 μm or less with respect to the depth of the holeprocessing. The description of the electric circuit, which is known, isomitted.

An embodiment of the touch sensor according to the invention has beendescribed above based on the drawings. However, the invention is notlimited to the illustrated embodiment, and with respect to the shape,feature, etc, of the invention, alterations such as variousmodifications in details and re-construction of parts may expectedly bemade within the scope of constituent features of the invention. Forexample, a drip proof function can be added by covering in a close-tightmanner the gap between the lock-washer 35 provided integrally with theanvil 34 and the flanged boss 43, by means of a thin flexible rubberbellows. The elastic wire materials 38 to cancel the weight m of themovable portion 28 may be replaced with a tension coil spring, acompression coil spring, a spring wire, or a piano wire. These elasticwire materials may be of beryllium copper or phosphor bronze. Theelastic wire materials 38 may be provided in such a manner that theplate spring 16 is suspended from the upper side or the plate spring 16is pressed up from the lower side. Instead of comprising the elasticwire materials 38, the plate spring 16 may be installed to inclineupwardly from the coupling member 18 to the coupling member 19, so thatthe self-weight of the plate spring 16, the coupling member, etc. willcause the plate spring 16 to be horizontal. Furthermore, a magneticallysensitive semiconductor such as a magneto resistance sensor may beemployed instead of the Hall IC 26. As a material of the elastic arm 16c, a material having flexibility such as polyester and film-like metalmay be employed instead of polyimide. Stainless, for example, may beemployed as a material for the aluminum alloy plate 17, and the platedoes not need to have a tabular shape. The installing positions of themagnet 25 and the Hall IC 26 may be mutually exchanged. In this case, itis preferred to provide the closing signal as a radio signal from theHall IC 26, which can lightweight the coupling member 19. Also, inaddition to or instead of lighting up the signal light 14 when theclosing signal is received, other notifying means may be used to notifythe reception of the closing signal, such as providing a speaker fromwhich a sound may be output to indicate the reception of the closingsignal.

INDUSTRIAL APPLICABILITY

The present invention may be used to check the machining positionthrough which the cutting edge of an edge tool advances, such as a biteand drill in an automated computer-controlled machine tool such as amachining center and jig drilling machine.

1. A touch sensor comprising, a first coupling member constructed in aunited manner with a pedestal, plate springs arranged to be paralleleach other, one end sides of the plate springs being fixed to both endsof the first coupling member respectively, a second coupling member tocouple other ends of the plate springs to each other, a magnet installedin a manner that the side of each plate spring corresponds to the sideof either magnetic pole, a pipe mounted to each plate springs inparallel to the direction of the magnetic poles of the magnet, and adetecting means located near the magnetic pole boundary line of themagnet for detecting a displacement of the magnet caused by an externalforce applied to the pipe, wherein the each plate has a rigid part withrigidity on the base end side, and an elastic part with elasticity onthe both end sides.
 2. A touch sensor as claimed in claim 1characterized by comprising an elastic body to cancel the effect ofgravity on the second coupling member.
 3. A touch sensor as claimed inclaim 1 or 2 characterized by comprising, a supporting member having oneend side fixed to the first coupling member and other end side providedwith the detecting means or the magnet, the supporting member inclinedfrom the one end side to the other end side, and an adjusting member foradjusting the distance between the supporting member and the pedestal,wherein the magnet or the detecting means is mounted to the secondcoupling member.
 4. A touch sensor as claimed in any of claims 1 to 3characterized in that holes are provided to portions where displacementis caused by an external force applied to the pipe.
 5. A touch sensor asclaimed in any of claims 1 to 4 characterized in that one end of thepipe is provided with a rigid anvil to receive an external force.
 6. Atouch sensor as claimed in any of claims 1 to 5 characterized bycomprising a notifying member for notifying whether or not a signal isoutput from the detecting means.
 7. A touch sensor as claimed in any ofclaims 1 to 6 characterized in that pedestals are provided to at leasttwo parts on a bottom surface of the pedestal.
 8. A touch sensor asclaimed in any of claims 1 to 7 characterized in that the pipe isprovided with a regulating member for regulating a displacement of pipebody.
 9. A touch sensor as claimed in any of claims 1 to 7 characterizedin that the pipe is provided so that its other end regulates adisplacement of the pipe body.